In an in vitro spinal cord preparation, our previous study and other reports have identified excitatory postsynaptic potentials (EPSPs) in motoneurons (MNs) evoked by ipsilateral dorsal root (iDR)[1], ipsilateral ventrolateral funiculus (iVLF)[2,3], and contralateral VLF (cVLF)[4] stimulation, i.e. iDR-EPSPs, iVLF-EPSPs and cVLF-EPSPs, respectively. But the long-term synaptic plasticity in these synaptic transmissions has been little studied yet. In the present study, the intracellular recordings were performed from MNs in neonatal rat (8-14 days old) spinal cord slices prepared by the previously described procedures under anaesthetized state with ether [5], and membrane electrical parameters were observed. By monitoring the multi-parameter changes of EPSPs after tetanic stimulation on iDR, iVLF or cVLF, efficiency of the excitatory synaptic transmission to MNs were estimated. The increase in EPSP amplitude to more than 120% of control level and at least for 30 min could be referred to as long-term potentiation (LTP). After tetanic stimulation on iDR in 26 MNs, LTP of iDR-EPSPs (i.e. iDR-LTP) was observed in 17 cells, without increase in amplitude of iVLF-EPSPs recorded simultaneously in the same MNs (n=15). Moreover, some relevant changes such as the increase of area under curve, the prolonging of duration and the shortening of latency of iDR-EPSPs but not of iVLF-EPSPs in 15 tested MNs were comparably noted during the iDR-LTP. Similarly, the tetanic stimulation on iVLF and cVLF induced LTP of iVLF-EPSP (iVLF-LTP) in 11 cells of 33 tested MNs, and of cVLF-EPSP (cVLF-LTP) in 2 MNs, respectively. It was also noted that in one MN with cVLF-LTP, the simultaneously recorded iDR-EPSPs were potentiated to reach the criteria for LTP either, suggesting a heterosynaptic LTP. Among 9 tested MNs with iVLF-LTP, the paired-pulse facilitation ratios of amplitude of iVLF-EPSPs elicited by paired-pulse stimulation were different from the baseline in 7 MNs. Considered as a whole, there were no significant changes in the membrane electrical parameters of the tested MNs following induction of LTP. These preliminary data suggest that there may be some forms of LTP in excitatory synaptic transmission from peripheral afferents and descending fibers to MNs in the spinal cord, and it could be considered as a candidate of neural basis underlying the ability of motor learning.